1. Field of the Invention
The present invention relates to a transmission interface conversion device and, more particularly, to a transmission interface conversion device that is easy to be installed and maintained and able to lower the production cost.
2. Description of the Related Art
In recent years, information transmitting and receiving has been widely employed in the industrial field because of the prosperous development in information network. For example, in an industrial manufacturing processing, various interfaces applicable for measuring, controlling, meter displaying, and information collecting are often implemented in an automatic system. All these interfaces require plenty of microprocessors. Among many designs of multipoint control unit (MCU) for middle-and-long distance communication, the interface of RS-485 is remarkable for its simple hardware design, easy manipulation, and low cost. Therefore, RS-485 has been broadly used in the fields such as factory automation, industry control, information supervision, and small-section supervision.
Moreover, the Electronic Industries Association (EIA) established a standard for RS-485 in 1983 on the basis of RS-422. The standard permits RS-485 to have multipoint and bi-directional communication, which allows multiple transmitters to be connected to the same bus. Meanwhile, drive power and conflict protection of the transmitters have been increased so that the range of bus sharing mode can be expanded as well. Therefore, the physical layer of a worksite bus in a present network used in an automatic control system, such as CAN, Profibus, INTERBUS-S and ARCNet, is doing the linking and researching jobs based on the bus of RS-485.
However, the interface of a conventional RS-485 needs four transmission lines, which include one pair of electric power transmission lines and another pair of signal transmission lines, to be connected to one master equipment controller and at least one slave device so as to carry out the transmission of electric power and signals. Therefore, if a lot of small-power devices have to be linked within a small area, the cable layout will become complicated and tedious, which often results in a higher cost in worksite cable layout. Moreover, with regard to the transmission method of conventional RS-485, if a transmission line is short-circuited or an open circuit is out of order, it will be difficult to find out what goes wrong. Besides, in case a node is not working, it may also stop the transmission line from transmitting.
Thus, the cost of cable layout for the conventional RS-485 interface will be high because of the above-mentioned expenses for the installation, labor, cables and maintenance. To cope with the problems, the present invention provides a new transmission interface conversion device to solve the conventional shortcomings.